As one of typical ceramic electronic components, there is a multilayer ceramic capacitor that has a structure as shown in, for example, FIG. 2.
This multilayer ceramic capacitor is, as shown in FIG. 2, structured to have external electrodes 54 (54a, 54b) provided, so as to be electrically connected to a plurality of internal electrodes 52 (52a, 52b), on both end surfaces 53a, 53b of a ceramic laminate (ceramic body) 60 obtained by laminating the internal electrodes 52 (52a, 52b) with ceramic layers 51 as dielectric layers interposed therebetween.
Now, in the case of manufacturing such a multilayer ceramic capacitor, it is common that the external electrodes (54a, 54b) are formed by a method of applying a conductive paste to both end surfaces of a ceramic laminate (ceramic body) and firing the paste.
As a conductive paste for use in the formation of such external electrodes, for example, a conductive paste including at least a metal powder and BaO—SrO—ZnO—B2O3—SiO2 based glass frit is proposed, in which the glass frit contains BaO: 10 to 50 weight %, SrO: 5 to 40 weight %, ZnO: 10 to 30 weight %, B2O3: 15 to 30 weight %, and SiO2: 3 to 20 weight % in terms of oxide, and the glass frit is contained at 0.5 to 10 weight % with respect to 100 weight % of the metal powder (see Patent Document 1).
Further, the formation of external electrodes with the use of the conductive paste is supposed to make the glass frit less likely to penetrate into the ceramic constituting the ceramic laminate during firing.
In addition, multilayer ceramic capacitors with external electrodes formed with the use of the conductive paste are supposed to be high in flexure strength and excellent in insulation resistance in high temperature load tests.
However, the conductive paste in Patent Document 1 has the problem of, because of the high ZnO content, making the ZnO likely to be eluted from the external electrodes into a plating solution when the external electrodes are subjected to Ni plating, Sn plating, or the like, and causing ingress of the plating solution from voids after the ZnO elution into the ceramic body constituting the multilayer ceramic capacitor, thereby decreasing the flexure strength of the multilayer ceramic capacitor.
In addition, the proportions of the SiO2 and B2O3 constituting the glass frit affect not only the plating resistance (plating solution resistance) of external electrodes formed, but also glass flotation of the glass component floated on the surfaces of the external electrodes and the densification of the external electrodes. In contrast, Patent Document 1 is not necessarily intended to clearly specify preferred proportions of the SiO2 and B2O3, it is thus difficult to achieve a balance among the plating resistance, the suppression of glass flotation, and the densification of external electrodes, and when external electrodes are formed with the use of the conductive paste in Patent Document 1, problems may be caused such as defective plating due to glass flotation and defective external connections. In addition, there are problems such as characteristics degraded or cracks caused by penetration of a plating solution or a cleaning solution from poorly densified external electrodes into the ceramic body constituting the multilayer ceramic electronic component.
Moreover, when the glass component in the external electrodes has an inappropriate composition, the glass component reacts with the ceramic constituting the ceramic body to form a reaction layer, thereby resulting in problems of crack generation and degraded flexure strength.
Patent Document 1: Japanese Patent Application Laid-Open No. 2003-77336